ML20246E007
| ML20246E007 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 08/21/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CP-89-006, CP-89-6, TXX-89594, NUDOCS 8908280363 | |
| Download: ML20246E007 (2) | |
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~ Log. # TXX-89594:
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fu 908.3' Ref. # 10CFR50.55(e) y 7t/ ELECTRIC WiHimm J. Cahill,Jr.
E;secutive Vice President U. 3. Nuclear Regulatory Commission Attn: Document Control Desk-Washington, D. C.
20555 i'
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 6.9KV BREAKER CHARGING MOTOR LINKAGE SDAR: CP-89-006 (FINAL REPORT)
Gentlemen:
On March-13,1989, TV Electric verbally notified the NRC staff of a deficiency involving the connecting linkage for the closing spring charging motors in the Class 1E 6.9kV switchgear. The last report was logged TXX-89188 and dated April 12, 1989. After further evaluation. TU Electric has concluded this deficiency. is reportable under the provisions of 10CFR50.55(e). The required information follows, Description As discussed in previous correspondence, this deficiency involved missing snap rings from a' pin in'the charging motor linkage to the breaker closing springs for the Class 1E 6.9kV switchgear. TXX-89188 provided a description of the deficiency, the initial corrective action being taken to resolve this issue, and also indicated that TU Electric would request the aid of the: vendor in determining the root cause of this deficiency and, based on the vendor's input, would access the adequacy of the initial corrective action and action to preclude recurrence.
. Discussions with the breaker vendor have disclosed that no other users of their equipment have reported similar problems, and that no such failures were experienced during endurance tests performed on these breakers at the vendor's facility.
Queries on the industry network were also inconclusive.
Based on this information it has been concluded that this deficiency was caused by a failure to install the snap ring, or a failure to ensure the snap ring was fully seated in the ring groove. This may have occurred during initial assembly or during breeker maintenance performed at CPSES.
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Ie TXX-89594 August 21, 1989 Page 2 of 2-Safety Implications Failure of Class IE 6.9kV breakers to remain functional af ter breaker cycling or the occurrence of internal breaker damage during breaker cycling due to binding of the disconnected linkage could adversely affect the safety of plant operations.
In addition, this deficiency represents.a significant deviation.
from performance specifications which required extensive evaluation to establish the adequacy of the Class IE 6.9kV breakers to perform their~
ir, tended safety functions. As a result, this deficiency meets the criteria for deportability pursuant to 10CFR50.55(e).
Corrective Action Based on reviews and discussions with the vendor, the corrective actions described in TXX-89188 are adequate to resolve this issue. To briefly summarize these corrective actions, they-involved inspection of the Class IE 6.9kV switchgear to ensure that each charging motor linkage pin has two undeformed snap rings fully seated in the snap ring grooves.
In addition, the Operations / Maintenance procedure for 6.9kV breaker inspection and cleaning has been revised to add a sign-off step for visual inspections of the charging motor linkage pin and snap rings.
Re-use of snap rings after removal is now prohibited.
As an additional step to preclude recurrence, appropriate procedures will be revised to provide for performance of a pre-installation inspection of 6.9kV switchgear breakers received at CPSES. The pre-installation inspections will assure that the snap rings are properly installed (i.e., no deformation exists and the snap rings are fully seated in the charging motor linkage pin grooves).
To date, inspections of the Unit 1 Trains "B" and "C" 6.9kV switchgear have l
been completed.
No additional examples of missing snap rings were identified.
l Train "A" inspections and the procedure revision discussed above will be I
completed prior to Unit I fuel load.
Inspections for Unit 2 will be l
completed prior to Unit 2 fuel load. This is the final report on this issue.
Sincerely, J-William J. Cahill, Jr.
WJH/vid c - Mr. R. D. Martin, Region IV Resident Inspectors, CPSES (3)
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